This invention relates to heat exchangers generally, and more specifically, to an exhaust gas heat exchanger for use in exhaust recirculation systems for internal combustion engines.
Heat exchangers useable in exhaust gas recirculation systems used with internal combustion engines, typically in vehicles, are known. One such heat exchanger is shown, for example, in German Patent Publication DE 101 24 383. While such heat exchangers work well for their intended function, heretofore, they have been constructed in a relatively expensive design that may lack flexibility, particularly where two exhaust channels are required.
The present invention is directed to providing a heat exchanger, and more particularly, the heat exchanger that may be utilized in an exhaust recirculation system that is economically fabricated and which can be readily utilized as a single channel or a multiple channel exhaust gas heat exchanger.
It is the principal object of the invention to provide a new and improved heat exchanger that may utilized in many heat exchange applications and which additionally is particularly suited for use in an exhaust gas recirculation system for internal combustion engines.
An exemplary embodiment of the invention envisions a heat exchanger that includes a plurality of elongated, straight, flat tubes. Each tube is formed of two identical halves joined to each other in mirror image fashion and each has opposed open ends. All of the tubes are arranged in a stack.
At least one spacer wall is disposed within each tube and extends generally from end to end thereof to define at least two side-by-side first fluid flow paths within each tube. Also provided is an elongated housing that contains the stack and which includes a header at each of two opposed ends. Each header includes a tube slot for the adjacent end of each tube in the stack and is sealed to each such adjacent end. Each header further is sealed to a corresponding end of each spacer wall in each tube in the stack and tube spacers are disposed in the stack separating adjacent tubes in the stack from one another and separating endmost tubes in the stack from the housing to define a second fluid flow path around the tubes and between the endmost tubes and the housing. The tube spacers include ribs defining a serpentine flow path for the second fluid. An opening is disposed in the housing near each end thereof and is in fluid communication with the second fluid flow path.
In a preferred embodiment, the tube halves are thin, channel-shaped plates or sheets having a base and the tube spacers are defined by deformations in the base.
Preferably, the tube spacers include small, nominally frusto-conical deformations in addition to the ribs.
In a preferred embodiment, each spacer wall comprises an elongated bar.
In one embodiment of the invention, a connection flange is located at each header.
In one embodiment, each connection flange and the corresponding header are integral.
In another embodiment, each connection flange and the corresponding header are plates in flush contact with each other and are joined together.
In a highly preferred embodiment, each connection flange has an opening spanned by braces that enter the second fluid flow path between the flat tubes at each end of the stack and which is sealed thereto.
In a highly preferred embodiment, the tube spacers are distributed along the entire length of each tube.
In one embodiment, the ribs are elongated and have a length less than the distance from an edge of each tube to the spacer wall therein and extend from the tube edge toward the spacer wall within the tube.
One embodiment of the invention contemplates that the openings in the housing wall are defined by slits in at least one wall of the housing and that there be a connection fitting sealed to the housing about each the slits.
In a highly preferred embodiment, each tube half is a thin, elongated, channel-shaped plate or sheet having a wide base and spaced, relatively short legs on each edge of the base. Each of the legs terminates in an outwardly directed flange defining a bonding area.
In a highly preferred embodiment of the invention, each outwardly directed flange has a plurality of outwardly extending tabs deformed over and engaging the adjacent outwardly directed flange of another tube half used to form each of the tubes.
Other objects and advantages will become apparent from the following specification taken in connection with the accompanying drawings.
The heat exchanger forming the invention hereof will described as a heat exchanger intended for use in an exhaust gas recirculation system for an internal combustion engine. However, those skilled in the art will recognize that it is susceptible to other uses as well and no limitation is intended to its use solely as an exhaust gas heat exchanger except as expressly stated in the appended claims. For example, the invention is susceptible to use wherever heat exchange between two fluids is required as, for example, as a liquid/gas heat exchanger.
Referring now to the drawings, and
Contained within the housing is a plurality of elongated, flat, tubes 16, arranged in a stack, generally designated 18. The tube stack 18 is provided with headers 20 at opposite ends of the tubes 18 which in turn are fitted with connection flanges 22, again at opposite ends of the housing 10.
Referring to
To establish fluid communication with the flow path 28, as best seen in
Returning to
In some cases, in lieu of the solid spacer bars 36, those skilled in the art will appreciate that the same thing could be accomplished by forming suitable ribs in the flat walls of each tube 16 which engage and are bonded to one another. However, spacer bars are preferred since the use of ribs or other spacer wall constructions requiring deformation of the tubes 16 may make it more difficult to obtain reliable sealing of the tubes at the headers 20 and connection flanges 22.
Referring to
The headers 20 may be integrally formed with the connection flanges 22 or may be flushly mounted thereagainst and bonded thereto.
As seen in
Each connection flange 42 also is provided with a series of openings 48 for receipt of threaded fasteners or the like whereby the heat exchanger, and in particular, the flow path defined by the tubes 16, may be connected into a fluid flow path of a heat exchange system.
Outwardly directed tabs 72 extend from each flange 70 and are folded over the abutting flange 70 to hold the tube halves 60,62 in an assembled state for bonding at the bonding area defined by each of the flanges 70.
The embossments or deformation 26 take on two forms. In one form 74, the embossments are much like dots, that is to say, they are nominally frusto-conical in shape. In another form 76, the embossments are elongated ribs which extend from one of the legs 66 or 68 transversely of the length of each of the tubes 16 to about the location of the spacer bars 36.
It is a principal feature of the invention that the tubes 16 be formed of two identical halves 60 and 62 so that they may be abutted to define a tube by placing them in mirror image fashion against one another with the flanges 70 abutting each other and defining a bonding area whereat the tube halves 60 and 62 may be bonded and sealed together, as by brazing or the like. The arrangement is such that the tube spacers, whether in the form shown at 74 or the form shown at 76 align with and abut each other so that they too may be bonded to one another.
In the case of the tube spacers 76, they are staggered extending from one side leg 66,68 toward the center to define a serpentine flow path indicated by a dotted arrow 82 in FIG. 7. In low pressure applications, only the rib 76 may be used while in higher pressure applications, the frusto-conical embossments 74 may be employed as well.
Because of the symmetry involved, when the tube halves 78,80 are assembled as shown in
From the foregoing, it will be appreciated that a very cost effective heat exchanger is provided by the invention. The use of identical tubes halves to define the tubes 16 as well as identical housing halves 12,13 minimize the tooling required to construct the same. The heat exchanger can provide two or more independent side-by-side fluid flow paths within the tubes simply by the use of one or more spacer bars 36 within each tube. Because of the ability to provide multiple flow paths within each tube 16, the same is ideally suited for those vehicular exhaust gas recirculating systems that require plural channels since the channels 54 are isolated from the channels 52 and may be set up as part of a separate flow path by appropriate connections to the connecting flanges 22 when the same is placed in the system.
Furthermore, if desired, a multipass flow system within the tube 16 could be provided simply by utilizing appropriate baffles at one or both of the headers 20 and connection flanges 22. The particular embodiment shown could be adapted to a two pass system simply by providing a baffle aligned with the spacer bars 36 separating an inlet to the flow channels 52 and an outlet from the flow channels 54 together with a cap or the like at the opposite connection flange 22 allowing fluid communication thereat between the flow channels 52 and 54. An even greater number of passes could be obtained by using an additional one or more spacer bars 36 within each one of the tubes 16.
If desired, turbulators or internal heat exchange enhancements, typically sinusoidal in shape, could be introduced into each of the flow channels 52 or 54 as schematically illustrated in dotted lines 90 in
The fact that the flow path 28 extends all the way about the tubes 16 and between the endmost tubes 16 in the stack and the housing 10 assures that the housing 10 will remain relatively cool when the flow path 28 is used as a coolant flow path as would be typical in an exhaust gas recirculation system application.
The ribs 76 provide an excellent fluid directing means within the flow path 28 and to this end, as seen in
In general, many of the components, including the headers 20 may be clad with a braze alloy to facilitate assembly. Where parts are not susceptible to being readily clad with a braze alloy, braze paste or foils may be located at the brazing areas. This technique would be particularly useful if the connection flanges 22 are made of a stainless steel, for example, which is not readily susceptible to braze cladding. Paste or foil would facilitate joining the connection flanges 22 to the headers 20 when the two are separate or in joining an integral header 20 and connection flange 22 to housing 36 and to the tubes 26.
In addition, the unique use of the spacer ribs 76 to direct flow, in the described embodiment, provides a means whereby either concurrent/cross or countercurrent/cross flow may be obtained with the flow path 28 as desired.
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102 14 467 | Mar 2002 | DE | national |
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Number | Date | Country | |
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20030196785 A1 | Oct 2003 | US |